Perhaps the most studied thermochemical water-splitting process is known as the sulfur-iodide process which operates at about 1000° C. This high temperature requirement cannot be reached economically with current-art concentrating solar thermal technologies, and does not allow the practical harvesting of thermal energy from other resources such as waste heat from turbines, low-quality combustible gases, and the like. Moreover, a process such as the Iodine-Sulfur process (I—S) operates with extremely corrosive materials. The expense of dealing with corrosion problems, as well as loss of a material as expensive as iodine, constitute significant drawbacks to using such a process.
Known low temperature processes, such as a copper chloride cycle require the use of silver chloride in its hydrogen cycle. Silver chloride is very expensive, and further, the silver must be removed and reprocessed in order to recover it. In a real world plant this fact alone guarantees unacceptable loses of silver. With silver at $80 per pound ($5.70/Tr Oz), and twice the molar requirement per mole of product hydrogen, the initial capital cost is commercially unacceptable. Moreover, it is possible that the silver losses alone could exceed the value of hydrogen produced.
Considerable interest in thermochemical water splitting cycles was shown in the 1960's and 70's when it was thought that heat from a nuclear reactor would be the source of energy and systems that had at least one high temperature step were widely explored. However, the practicality of using a nuclear power plant for the purpose of making hydrogen did not take into account the other more profitable uses of that heat. Furthermore, nuclear power has steadily fallen out of favor in the U.S. A key factor that was over-looked was the high temperatures required presented serious problems including the use of construction materials. This alone doomed most of the proposed systems. While the prospect of utilizing a high temperature seemed promising insofar as it could open the door to many reactions and possibly high rates, after examination of many potential cycles, the flaws which inherent in them became all too apparent, and none have been commercialized.
It is an object of the present invention to chose selectively, scaleable reactions at as low a temperature as possible to achieve a truly useful process that can utilize, among other sources, waste heat and thereby increase the efficiency of many energy sources as well as produce inexpensive hydrogen and oxygen.